It doesn't make sense to wrap something that isn't a Java interface as an Xcore interface. Also, if you want to use the classifier to define a non-transient attribute's type, you need to use a data type, not a class/interface. There is no support for wrapping an existing enum as anything another than a data type. I.e., an EEnum/xEnum can't be a wrapper. So you can use "type Foo wraps A.b.c" and you can define the create/convert operations in the type definition. Ctrl-Space is your friend.